You change inserts if the paint you're using can fall straight through. The insert should grip the ball and you should be able to use your mouth to blow it out. Perhaps you should get a few other sizes, a larger one in case you use larger bored paint.

You change inserts if the paint you're using can fall straight through. The insert should grip the ball and you should be able to use your mouth to blow it out. Perhaps you should get a few other sizes, a larger one in case you use larger bored paint.

No, neither of the bores is more accurate by any means. The .684 is larger, so use that if you want to overbore your paint, which by no means is a bad thing; it gives you better consistency with the drawback of an ever-so-slight drop in efficiency. If you want to undebore it, then go right ahead; it'll give you more efficiency with slightly less consistency. You choose what you want, they hardly make a difference.

Here's the bottomline: there are only two kinds of bores that will screw you over. The two kinds of bores listed below are what you want to AVOID:
1) Paint to barrel matching. This is actually what Vidalecent is describing. If the bore of the paint matches the bore of the barrel, you get wildly inconsistent shots because paint is wildly inconsistent sizes. One will match, the next will fit snug and go faster, and the next will be smaller and air will pass by making it slower. This is the least consistent of all bores and what you should avoid.
2) SEVERE unboring. A slight to medium underbore is fine, and actually can result in the best attributes for those who care about efficiency. However a severe underbore (by .008 or more) can begin to lead to paint breakages in your barrel. Most paint these days won't be large enough to result in this happening, but it can be an issue. The tolerances get worse as the paint gets more brittle and the temperature drops. I would recommend an underbore of .005 or smaller due to this, but the evidence as to the exact number is only anecdotal in the poor conditions I mentioned.

Here is what you want:
1) Small to medium underbore. This will give you the best consistency and efficiency. Unlike the bore matching, every ball will seal with the barrel and you'll get great consistency, and unlike a SEVERE underbore, you won't break much paint.
2) Overbore. This is what I use. It's easy as pie and you never have to worry about it. It's as consistent as a small to medium underbore, but it loses out a good deal (10-20%) on efficiency. Since I have easy fill-ups, I don't care about consistency that much so I just go with it since I'll never have to change my barrel and it will always work regardless of conditions.

No, neither of the bores is more accurate by any means. The .684 is larger, so use that if you want to overbore your paint, which by no means is a bad thing; it gives you better consistency with the drawback of an ever-so-slight drop in efficiency. If you want to undebore it, then go right ahead; it'll give you more efficiency with slightly less consistency. You choose what you want, they hardly make a difference.

Nope, an underbore will be more consistent, and efficient, and an overbore will be more quiet.

No, neither of the bores is more accurate by any means. The .684 is larger, so use that if you want to overbore your paint, which by no means is a bad thing; it gives you better consistency with the drawback of an ever-so-slight drop in efficiency. If you want to undebore it, then go right ahead; it'll give you more efficiency with slightly less consistency. You choose what you want, they hardly make a difference.

Nope, an underbore will be more consistent, and efficient, and an overbore will be more quiet.

Haha messed up, I knew that. It was late for me and I was stressed from classes.

Here's the bottomline: there are only two kinds of bores that will screw you over. The two kinds of bores listed below are what you want to AVOID:1) Paint to barrel matching. This is actually what Vidalecent is describing. If the bore of the paint matches the bore of the barrel, you get wildly inconsistent shots because paint is wildly inconsistent sizes. One will match, the next will fit snug and go faster, and the next will be smaller and air will pass by making it slower. This is the least consistent of all bores and what you should avoid.2) SEVERE unboring. A slight to medium underbore is fine, and actually can result in the best attributes for those who care about efficiency. However a severe underbore (by .008 or more) can begin to lead to paint breakages in your barrel. Most paint these days won't be large enough to result in this happening, but it can be an issue. The tolerances get worse as the paint gets more brittle and the temperature drops. I would recommend an underbore of .005 or smaller due to this, but the evidence as to the exact number is only anecdotal in the poor conditions I mentioned.

Here is what you want:1) Small to medium underbore. This will give you the best consistency and efficiency. Unlike the bore matching, every ball will seal with the barrel and you'll get great consistency, and unlike a SEVERE underbore, you won't break much paint.2) Overbore. This is what I use. It's easy as pie and you never have to worry about it. It's as consistent as a small to medium underbore, but it loses out a good deal (10-20%) on efficiency. Since I have easy fill-ups, I don't care about consistency that much so I just go with it since I'll never have to change my barrel and it will always work regardless of conditions.